The proper control of pain is one of the most important areas in health care. We still rely heavily on opioid narcotics for acute and chronic pain control despite growing evidence of their risks and lack of strong efficacy. In surgical populations, where opioid prescribing is common and often believed to be good practice, the amount and duration of post-operative opioid prescriptions are strongly related to subsequent opioid misuse, and perioperative opioid use is associated with increased morbidity and mortality. Total knee arthroplasty (TKA) is one of the most common orthopaedic procedures performed. While knee pain is often a complaint that precedes TKA, the procedure itself is associated with considerable post-operative pain lasting days to weeks. Data suggest that adequate post-operative pain control in this population is an important factor in determining surgical outcomes, recovery time, and hospital length of stay. While the technology associated with the TKA procedure itself has developed rapidly in the past several years, post-operative pain management techniques have not changed substantially in several decades, and despite the currently employed pain-management strategies, patients still report considerable post-operative pain, and often struggle to complete post-operative physical therapy regimens. New analgesic strategies are needed that can be used adjunctively with existing strategies that have the potential to reduce reliance on opioid analgesia, and reduce post-operative pain. Several novel brain stimulation technologies including transcranial direct current stimulation (tDCS) are beginning to demonstrate promise as treatments for a variety of pain conditions including perioperative pain. In a series of recent studies, the PI has shown that tDCS can reduce post-operative opioid use by as much as 43% while simultaneously reducing subjective pain ratings. This recent scientific work (and the work of others) suggests that stimulating pain-modulating areas of the human cortex with tDCS has the potential to yield meaningful analgesic effects and reduce post-operative opioid consumption with minimal risks or side-effects. Another non-pharmacologic approach to pain-management with minimal risks and good potential benefit is cognitive behavioral therapy for pain (CBT-P). CBT-P has consistently demonstrated solid empirical support as an effective treatment for chronic pain, but it is less well-studied in perioperative settings. Nonetheless, a few small studies have demonstrated that brief cognitive-behavioral interventions hold promise as adjunctive post- operative pain management strategies, but more work is needed. Interestingly, accumulating data from our group suggest that tDCS of the prefrontal cortex may augment the analgesic effects of cognitive-behavioral (CB) interventions for acute pain. When combined with a brief cognitive-behavioral intervention for acute pain, tDCS appears to enhance the analgesic benefits of the cognitive-behavioral intervention while improving participants? subjective capacity to benefit from it. It appears that tDCS may be able to prime neural circuits that facilitate engagement of brain areas involved with pain-reducing cognitions and behavioral patterns. Thus, when cognitive-behavioral pain management strategies are taught to patients during tDCS, more analgesic benefit is observed than with either intervention alone. To date, no studies to date have directly investigated analgesic benefits of combining these approaches in the post-operative arena. The proposed study will be the first ever to (1) determine the independent effects of post-operative tDCS and a brief cognitive-behavioral intervention on post-operative pain, opioid use and functioning following TKA, (2) determine the effects of combining tDCS with a brief cognitive-behavioral intervention, and (3) determine longer-term outcomes of post-operative tDCS and a cognitive-behavioral intervention on pain, opioid use, quality of life, and functioning in TKA patients. This innovative, high-quality clinical trial has the potential to generate findings that could shift the modern paradigm of post-operative pain management to take advantage of recent neuroscience and behavioral-science developments.